String formatting consolidated and inheritance of BigDecimal from IFo…

…rmattable

src/Deveel.Math/Math/BigDecimal_Convertible.cs

@@ -42,7 +42,7 @@ bool IConvertible.ToBoolean(IFormatProvider provider)
 
         byte IConvertible.ToByte(IFormatProvider provider)
         {
-            int value = ToInt32Exact();
+            var value = ToInt16Exact();
             if (value > Byte.MaxValue || value < Byte.MinValue)
                 throw new InvalidCastException();
 
@@ -51,23 +51,23 @@ byte IConvertible.ToByte(IFormatProvider provider)
 
         short IConvertible.ToInt16(IFormatProvider provider)
         {
-            var value = ToInt16Exact();
+            var value = ToInt32Exact();
             if (value > Int16.MaxValue || value < Int16.MinValue)
                 throw new InvalidCastException();
 
-            return value;
+            return (short) value;
         }
 
         ushort IConvertible.ToUInt16(IFormatProvider provider) => throw new NotSupportedException();
 
         // TODO: use the IFormatProvider
         int IConvertible.ToInt32(IFormatProvider provider)
         {
-            var value = ToInt32Exact();
+            var value = ToInt64Exact();
             if (value > Int32.MaxValue || value < Int32.MinValue)
                 throw new InvalidCastException();
 
-            return value;
+            return (int)value;
         }
 
         // TODO: verify if it is possible to convert to uint
@@ -112,7 +112,7 @@ decimal IConvertible.ToDecimal(IFormatProvider provider)
 
         string IConvertible.ToString(IFormatProvider provider)
         {
-            return ToString(provider);
+            return ToString(GeneralStringFormat, provider);
         }
 
         object IConvertible.ToType(Type conversionType, IFormatProvider provider)
@@ -134,106 +134,6 @@ public override string ToString()
             return ToString(null);
         }
 
-        /// <summary>
-        /// Converts this <see cref="BigDecimal"/> to a string representation
-        /// </summary>
-        /// <param name="provider"></param>
-        /// <returns></returns>
-        public string ToString(IFormatProvider provider)
-        {
-            if (provider == null)
-                provider = NumberFormatInfo.InvariantInfo;
-
-            return DecimalString.ToString(this, provider);
-        }
-
-        // TODO: use a IFormattable for the Engineering and the Plain string
-
-        /// <summary>
-        /// Returns a string representation of this number,
-        /// including all significant digits of this value
-        /// </summary>
-        /// <remarks>
-        /// <para>
-        /// If the scale is negative or if <c>scale - precision >= 6</c> 
-        /// then engineering notation is used. Engineering notation is 
-        /// similar to the scientific notation except that the exponent 
-        /// is made to be a multiple of 3 such that the integer part 
-        /// is lesser or equal to 1 and greater than 1000.
-        /// </para>
-        /// <para>
-        /// This overload uses the invariant culture to resolve the
-        /// format information for the string.
-        /// </para>
-        /// </remarks>
-        /// <returns>
-        /// Returns a string representation of this number in engineering 
-        /// notation if necessary.
-        /// </returns>
-        public String ToEngineeringString()
-        {
-            return ToEngineeringString(null);
-        }
-
-        /// <summary>
-        /// Returns a string representation of this number,
-        /// including all significant digits of this value
-        /// </summary>
-        /// <param name="provider">The provider used to resolve the
-        /// format information to use.</param>
-        /// <remarks>
-        /// <para>
-        /// If the scale is negative or if <c>scale - precision >= 6</c> 
-        /// then engineering notation is used. Engineering notation is 
-        /// similar to the scientific notation except that the exponent 
-        /// is made to be a multiple of 3 such that the integer part 
-        /// is greater or equal than 1 and is smaller than 1000.
-        /// </para>
-        /// </remarks>
-        /// <returns>
-        /// Returns a string representation of this number in engineering 
-        /// notation if necessary.
-        /// </returns>
-        public String ToEngineeringString(IFormatProvider provider)
-        {
-            if (provider == null)
-                provider = NumberFormatInfo.InvariantInfo;
-
-            return DecimalString.ToEngineeringString(this, provider);
-        }
-
-        /// <summary>
-        /// Returns a string representation of this <see cref="BigDecimal"/>
-        /// as a plain number, without any scientific notation.
-        /// </summary>
-        /// <param name="provider"></param>
-        /// <remarks>
-        /// <para>
-        /// This methods adds zeros where necessary.
-        /// </para>
-        /// <para>
-        /// If the string representation is used to create a new instance, this
-        /// instance is generally not identical to this instance as the precision
-        /// changes.
-        /// </para>
-        /// </remarks>
-        /// <returns>
-        /// Returns a string representation of this number without any
-        /// exponent part.
-        /// </returns>
-        public String ToPlainString(IFormatProvider provider)
-        {
-            if (provider == null)
-                provider = CultureInfo.InvariantCulture;
-
-            return DecimalString.ToPlainString(this, provider);
-        }
-
-        public String ToPlainString()
-        {
-            return ToPlainString(null);
-        }
-
         /// <summary>
         /// Converts this <see cref="BigDecimal"/> to a <see cref="BigInteger"/>
         /// instance, discarding any fractional part.
@@ -400,6 +300,11 @@ public short ToInt16Exact()
             return (short)ValueExact(16);
         }
 
+        public byte ToByteExact()
+        {
+            return (byte)ValueExact(8);
+        }
+
         /**
 		 * Returns this {@code BigDecimal} as a byte value if it has no fractional
 		 * part and if its value fits to the byte range ([-128..127]). If these
@@ -410,9 +315,9 @@ public short ToInt16Exact()
 		 *             if rounding is necessary or the number doesn't fit in a byte.
 		 */
 
-        public byte ToByteExact()
+        public sbyte ToSByteExact()
         {
-            return (byte)ValueExact(8);
+            return (sbyte)ValueExact(8);
         }
 
         /// <summary>
@@ -461,26 +366,49 @@ public float ToSingle()
             return floatResult;
         }
 
-         ///**
-		 //* Returns this {@code BigDecimal} as a double value. If {@code this} is too
-		 //* big to be represented as an float, then {@code Double.POSITIVE_INFINITY}
-		 //* or {@code Double.NEGATIVE_INFINITY} is returned.
-		 //* <p>
-		 //* Note, that if the unscaled value has more than 53 significant digits,
-		 //* then this decimal cannot be represented exactly in a double variable. In
-		 //* this case the result is rounded.
-		 //* <p>
-		 //* For example, if the instance {@code x1 = new BigDecimal("0.1")} cannot be
-		 //* represented exactly as a double, and thus {@code x1.equals(new
-		 //* BigDecimal(x1.ToDouble())} returns {@code false} for this case.
-		 //* <p>
-		 //* Similarly, if the instance {@code new BigDecimal(9007199254740993L)} is
-		 //* converted to a double, the result is {@code 9.007199254740992E15}.
-		 //* <p>
-		 //*
-		 //* @return this {@code BigDecimal} as a double value.
-		 //*/
+        ///**
+        //* Returns this {@code BigDecimal} as a double value. If {@code this} is too
+        //* big to be represented as an float, then {@code Double.POSITIVE_INFINITY}
+        //* or {@code Double.NEGATIVE_INFINITY} is returned.
+        //* <p>
+        //* Note, that if the unscaled value has more than 53 significant digits,
+        //* then this decimal cannot be represented exactly in a double variable. In
+        //* this case the result is rounded.
+        //* <p>
+        //* For example, if the instance {@code x1 = new BigDecimal("0.1")} cannot be
+        //* represented exactly as a double, and thus {@code x1.equals(new
+        //* BigDecimal(x1.ToDouble())} returns {@code false} for this case.
+        //* <p>
+        //* Similarly, if the instance {@code new BigDecimal(9007199254740993L)} is
+        //* converted to a double, the result is {@code 9.007199254740992E15}.
+        //* <p>
+        //*
+        //* @return this {@code BigDecimal} as a double value.
+        //*/
 
+        /// <summary>
+        /// Converts this <see cref="BigDecimal"/> to a <see cref="double"/>.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// If the <see cref="BigDecimal"/> is too big to be represented as an float, 
+        /// then <see cref="Double.PositiveInfinity"/> or <see cref="Double.NegativeInfinity"/> 
+        /// is returned.
+        /// </para>
+        /// <para>
+        /// Note, that if the unscaled value has more than 53 significant digits, then this decimal 
+        /// cannot be represented exactly in a double variable. In this case the result is rounded.
+        /// </para>
+        /// <para>
+        /// For example, if the instance <c>x1 = BigDecimal.Parse("0.1")</c> cannot be
+        /// represented exactly as a double, and thus <c>x1.Equals(new BigDecimal(x1.ToDouble())</c> 
+        /// returns <c>false</c> for this case.
+        /// </para>
+        /// <para>
+        /// Similarly, if the instance <c>new BigDecimal(9007199254740993L)</c> is converted to a 
+        /// double, the result is <c>9.007199254740992E15</c>.
+        /// </para>
+        /// </remarks>
         public double ToDouble()
         {
             int sign = Sign;

src/Deveel.Math/Math/BigDecimal_Formattable.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Globalization;
+
+namespace Deveel.Math
+{
+    public sealed partial class BigDecimal : IFormattable
+    {
+        private const string GeneralStringFormat = "G";
+        private const string PlainStringFormat = "P";
+        private const string EngineeringStringFormat = "E";
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="format"></param>
+        /// <param name="provider"></param>
+        /// <remarks>
+        /// <para>
+        ///     The supported formats are
+        ///     <list type="bullet">
+        ///         <listheader>
+        ///           <term>Format</term>
+        ///           <description>Description</description>
+        ///         </listheader>
+        ///         <item>
+        ///             <term><c>G</c></term>
+        ///             <description>General format. The number is formatted as a fixed-point number.</description>
+        ///         </item>
+        ///         <item>
+        ///             <term><c>P</c></term>
+        ///             <description>Plain format. The number is formatted as a plain number, without any scientific
+        ///             notation. If the string representation is used to create a new instance, this instance is 
+        ///             generally not identical to this instance as the precision</description>
+        ///         </item>
+        ///         <item>
+        ///             <term><c>E</c></term>
+        ///             <description>Engineering format. The number is formatted as a fixed-point number in engineering
+        ///             notation. If the scale is negative or if <c>scale - precision >= 6</c> 
+        ///             then engineering notation is used. Engineering notation is similar to the scientific notation except 
+        ///             that the exponent is made to be a multiple of 3 such that the integer part is lesser or equal to 1 
+        ///             and greater than 1000.</description>
+        ///         </item>
+        ///     </list>
+        /// </para>
+        /// </remarks>
+        /// <returns></returns>
+        /// <exception cref="ArgumentException"></exception>
+        public string ToString(string? format, IFormatProvider? provider = null)
+        {
+            if (provider == null)
+                provider = NumberFormatInfo.CurrentInfo;
+
+            if (String.IsNullOrWhiteSpace(format) ||
+                format == GeneralStringFormat)
+            {
+                return DecimalString.ToString(this, provider);
+            } else if (format == PlainStringFormat)
+            {
+                return DecimalString.ToPlainString(this, provider);
+            } else if (format == EngineeringStringFormat)
+            {
+                return DecimalString.ToEngineeringString(this, provider);
+            }
+
+            throw new ArgumentException($"Format '{format}' was not recognized");
+        }
+    }
+}