prog:     stmts;

prog: [ vars ] funs;

vars: 'var' names ';';

names: Name [{ ',' Name }];

funs: { fun };

fun: head [ 'begin' stmts 'end' ] ';';

head: 'function' Name;

stmts:    stmt [{ ';' stmt }];

stmts: stmt [{ ';' stmt }];

stmt:     assign | print | loop | select;

stmt: assign | print | return | loop | select;

assign:   Name '=' sum;

assign: Name [ '=' sum ];

print:    'print' sums;

print: 'print' sums;

sums:     sum [{ ',' sum }];

sums: sum [{ ',' sum }];

return: 'return' [ sum ];

loop:     While cmp Do stmts 'od';

loop: While cmp Do stmts 'od';

While:    'while';

While: 'while';

Do:       'do';

Do: 'do';

select:   'if' cmp Then stmts [ Else stmts ] 'fi';

select: 'if' cmp Then stmts [ Else stmts ] 'fi';

Then:     'then';

Then: 'then';

Else:     'else';

Else: 'else';

cmp:      sum rel;

cmp: sum rel;

rel:      eq | ne | gt | ge | lt | le;

rel: eq | ne | gt | ge | lt | le;

eq:       '=' sum;

eq: '=' sum;

ne:       '<>' sum;

ne: '<>' sum;

gt:       '>' sum;

gt: '>' sum;

ge:       '>=' sum;

ge: '>=' sum;

lt:       '<' sum;

lt: '<' sum;

le:       '<=' sum;

le: '<=' sum;

sum:      product [{ add | subtract }];

sum: product [{ add | subtract }];

add:      '+' product;

add: '+' product;

subtract: '-' product;

subtract: '-' product;

product:  signed [{ multiply | divide }];

product: signed [{ multiply | divide }];

multiply: '*' signed;

multiply: '*' signed;

divide:   '/' signed;

divide: '/' signed;

signed:   [ '-' ] term;

signed: [ '-' ] term;

term:     input | number | name | '(' sum ')';

term: input | number | name | '(' sum ')';

input:    'input' [ Number ];

input: 'input' [ Number ];

number:   Number;

number: Number;

name:     Name;

name: Name;