A comment is preceded by the # character. Everything after a # is ignored up to the end of the line. For example,
# This is a comment
var i = 1 + 2 # this is also a comment
There are no special multi-line comments. If you want to comment out an entire block of code, you must prefix each line with a # character. That is
# This is a multi-line
# comment.
var i = 1 + 2
Repeats a group of statements for each index in a range.
for counter in start loop_type end [by step_val] do
[ statements ]
end
- counter is required. The control variable for the loop.
- start is required. The starting value for the control variable.
- loop_type is required. Determines how the counter steps through the range. Permitted values are to and until. to means the loop range is [start, end] while until means the loop range is [start,end).
- by is optional. If it is specified, the counter is incremented by step_val.
Examples:
for i in 0 until 2 do
print("value of i: %d\n", i)
end
value of i: 0
value of i: 1
for i in 1 to 5 by 2 do
print("value of i: %d\n", i)
end
value of i: 1
value of i: 3
value of i: 5
In Contra, a function is a group of statements that is given a name, and which can be called from some point of the program. The syntax to define a function is:
function name ( parameter1, parameter2, ...) -> type
statements
return statement
end
Where:
- type is the type of the value returned by the function.
- name is the identifier by which the function can be called.
- parameters (as many as needed): Each parameter consists of an identifier followed by a colon and then a type, with each parameter being separated from the next by a comma. For example:
x : i64. These parameters are local to the function. - statements is the function's body. It is a block of statements surrounded by the function signature and end that specify what the function actually does.
Only one return statement is allowed, and it must occur at the end of the function. The return type specifier is optional. A function that has no return type looks like
function name ( parameter1, parameter2, ...)
statements
end
Conditionally executes a group of statements, depending on the value of an expression.
if (condition) then
[ statements ]
[ elif (elseifcondition) then
[ elseifstatements ] ]
[ else
[ elsestatements ] ]
end
- condition is required. It must evaluate to true or false.
- *then is required.
- statements are optional. One or more statements following if...then that are executed if condition evaluates to true.
- elseifcondition is required if elif is present. Must evaluate to true or false.
- elseifstatements are optionsal. One or more statements following elif...then that are executed if elseifcondition evaluates to true.
- elsestatements are optional. One or more statements that are executed if no previous condition or elseifcondition expression evaluates to true.
- end is requred.
Example:
if (number % 15 == 0) then
print("fizzbuzz %d\n", number)
elif (number % 5 == 0) then
print("buzz %d\n", number)
elif (number % 3 == 0) then
print("fizz %d\n", number)
else
print("%d\n", number)
end
Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers.
print( format, ... )
print secretly calls the C built-in printf function. So format may contain any of the same format specificers. See the manual for printf.
Example:
print("Decimals: %lld\n", 650000)
print("Preceding with blanks: %10lld \n", 1977)
print("Preceding with zeros: %010lld \n", 1977)
print("floats: %4.2f %+.0e %E \n", 3.1416, 3.1416, 3.1416)
print("%s \n", "A string")
Outputs:
Decimals: 650000
Preceding with blanks: 1977
Preceding with zeros: 0000001977
floats: 3.14 +3e+00 3.141600E+00
A string