p0 language definition

Variables a-z (.data segment) of size 1 word.

Statements

• stmt -> <var> = expr
• expr -> <var> expr | <const> expr | op expr | ε
• op -> + | - | * | / | % | > | => | < | =< | == | =! | & | |

I/O

• :getchar(var)
• :putchar(var)
• :uchar(var) - putchar for stderr
• :raw(constant string)
• :throw(constant string) - raw for stderr

var is destination/source, always read stdin and write stdout. raw is utility function that prints out a string constant.

Execution flow

• :if(expr){} else{}
• :while(expr){}

Exit

• :exit(expr)

Memory

Load or store value into/from 1st arg, at index in memory array determined by 2nd arg. Load needs a variable as 1st argument (destination).

• :load(var,expr)
• :store(expr,expr)

Functions

Definition

• :fun(name){}

Call

• :call(name)

Extra

Parsing

: is at the beginning of all special functions, after which only the first character is checked (:call and :c behave the same).

Syntax weirdness

Don’t add extra spaces/characters inside keyword calls. Don’t write an empty if block and an else in the same line. Closing brace and else must also be in the same line. If in doubt, check how its done in prev.p0. The syntax is not very robust, and that was kind of the point.

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