Basic specification for the language.

Discussion about (anti-)features (this section should remain confidential)

• simple tokens (easy lexer, because lexers are boring)
• complex grammar
  • no mandatory parentheses, no separator
  • parentheses for value expression, boolean expression and blocks of statement (instead of brackets)
  • = is both assignment and comparison
  • comparison can be combined a = b = c means a = b && b = c
  • => should be hasr to parse with dirty regexp or a manual recursive ll parser. Most tools should be able to deal with the language.
• doable evaluation
  • standard statement and expressions
  • the combined comparisons is the most tricky
• possible compiler to C
  • generating C code is mainly trivial
  • the combined comparisons is the most tricky

Syntax

Program files are ASCII 7 bits.

Characters <= 32 are ignored and considered valid separators.

Keywords print, byte, println, while, if, read and not. They are case-sensitive, reserved and unusable as identifier Other sequence of letters (a-z and A-Z) are valid identifier (no digit)

Sequence of digits are considered a literal number

Program and Statements

A program is made of a sequence of statements

Assignment

syntax: *identifier* = *value*

examples:

a = 5
foo = a + 5

Printing

syntaxes: print *string* or print [byte] value or println

examples:

print "hello"
print 42
print byte 42
println

Sequence

Sequences of statements are executed in order

exemples:

a = 1 print "a=" print a println
a=1print"a="print a println

Multiple statements can be grouped together with parentheses

(a = 1 print "a=" print a println)

While

syntax: while *condition* *statement*

example:

a = 5
while a>0 (print "*" a = a - 1)

If

syntax: if *condition* *statement* [else *statement*]

example:

a = 5
if a > 0 print "ok"
if a < 0 print "fail"
if a = 5 print "ok" else print "fail"

Values

values are signed integers with at least 16 bits of precision.

Literal

can be standard decimal representation or ASCII 7 bits character (ascii code is used)

Variables

scope is global. using a unassigned variable is undefined.

Basic arithmetic operators

• infix binary operators + - * /
• the unary - for the negation.
• parenthese for grouping an priority
• Standard priority and associativity.

Read

syntax read and read byte

Contition

Comparaison

syntax: *value* [*op* *value*]+

where op is on of = != < <= > >=

examples

a = 1
b = 2
if a = 1 != b < 4 print "ok"
if a = 1 != b = 4 print "fail"

Boolean operations

The three booleam operators ||, && and not can be used. precedence is left to right, || begin the least and not the most. PArentherses can bu used for grouping and priority again.

examples:

a = 5
if a > 2 && a < 7 print "ok"
if not (a < 2 || a > 7) print "ok"