Documentation

Statements

output [expression]

input [variable]

input [variable] prompt [string]

set [variable] to [expression]

if [boolean_expression] then
    [statement_1]
    . . .
    [statement_n]
endif

if [boolean_expression] then
    [statement_A1]
    . . .
    [statement_An]
else
    [statement_B1]
    . . .
    [statement_Bn]
endif

if [boolean_expression_A] then
    [statement_A1]
    . . .
    [statement_An]
elseif [boolean_expression_B] then
    [statement_B1]
    . . .
    [statement_Bn]

. . . 

else
    [statement_N1]
    . . .
    [statement_Nn]
endif

while [boolean_expression] do
    [statement_1]
    . . .
    [statement_n]
endwhile

Variables

A variable is a named area of memory that can hold one value. A variable name can be any sequence of letters {a-z, A-Z}, digits {0-9}, and the underscore {'_'}, subject to two restrictions:

It cannot begin with a digit; and

It cannot be a SPL keyword (a word reserved by SPL itself). The following eighteen keywords are not allowed:

    and       do     else     elseif    endif    endwhile
    false     if     input    not       or       output
    prompt    set    then     to        true     while

Expressions

An expression can be

a string, such as "Hello World!" or "3 + 4 = 7" or "The word 'and' is reserved"; or
a number, such as 2, 14.9, -0.5, 4.1e8; or
a boolean value - one of the words true or false
a variable; or
one or more of the above modified by an operator

Examples of Expressions (using output statement)

Statement(s)	What is Displayed
output "Hello World!"	Hello World!
output 3	3
output 3 + 4	7
output "3 + 4"	3 + 4
output "3 + 4 = " & 3 + 4	3 + 4 = 7
set x to 7 output x * 9	63
output 2 + 3 < 4	false
output 2 < 5 and 5 < 8	true

Operators

The SPL operators are shown below, listed from highest precedence to lowest. (All operators on the same row have equal precedence.)

Operator	Associativity	Name/Function
( )	inner-to-outer	Parentheses
^	right-to-left	Exponentiation
-	right	Unary Minus
*, /, //, %	left-to-right	Multiplication, Division, Integer Division, Remainder
+, -	left-to-right	Addition, Subtraction
=, !=, <, <=, >, >=	none	Equal, Not Equal, Less Than, Less Than or Equal, Greater Than, Greater Than or Equal
not	right	Negation
and	left-to-right	Conjunction
or	left-to-right	Disjunction
&	left-to-right	String Concatenation

Associativity indicates the execution order when an expression contains multiple operators with equal precedence. For example:

Addition and subtraction have equal precedence. Since their associativity is left-to-right, the expression 5 - 2 + 3 means (5 - 2) + 3.
Since the associativity of exponentiation is right-to-left, the expression 5 ^ 2 ^ 3 means 5 ^ (2 ^ 3).

Note on Integer Division (the "//" Operator)

When two numbers are divided using integer division, the result is the whole number part of the answer - i.e., the part to the left of the decimal point.

In other words, the result is truncated, not rounded.

Examples

Division	Result
6 // 3	2
5 // 3	1
4 // 3	1
3 // 3	1
2 // 3	0

Useful Tip: if a < b, then a // b = 0.

Comments

The hash sign '#' indicates a comment in SPL. Anything appearing after '#' until the end of the line will be ignored.

White Space

Ordinary spaces are required to separate SPL keywords from other tokens. All other white space, while usually helpful, is optional. So, spaces are not required to separate operators from their operands, line breaks are not required to separate statements, and no indentation is required to determine scope.

For example, the following two programs are equivalent (they both display the values of 2ⁿ - 1, for n from 1 to 12):

set n to 1 
while n <= 12 do 
    output 2 ^ n - 1 
    set n to n + 1 
endwhile

set n to 1 while n<=12 do output 2^n-1 set n to n+1 endwhile