Hi! I'm writing a java library for programatically
building circuits of sound processing units. It's mainly
a wrapper to csound. From the circuit a csound
orc is generated. Each unit correspond to a
csound opcode and has ports corresponding to the
opcode parameters/outputs. I'm allowing the
construction of units from csound expressions
too. A unit of this kind has input ports for the
variables in the expression and one output port.
I need to parse and validate the expression. I have
metadata in XML describing csound opcodes already,
which I use to create the opcode units. This
metadata indicates number of params, their
rates, etc. But I'm not sure
if I can treat opcodes and operators (the
ones with functional syntaxis, as sin) the same
and use this metadata for both validation of
circuits and expressions.
Below are two detailed questions to which
I couldn't find a definite answer. Please
I need your help.

Thank you in advance.
Regards, Carlos.


1) From "The Canonical Csound Reference Manual":

"""
Thoughout this manual, the term "opcode" is used
to indicate a command that usually produces an
a-, k-, or i-rate output, and always forms the
basis of a complete Csound orchestra statement.
Items such as "+" or "sin(x)" or,
"( a >= b ? c : d)" are called "operators."
"""

Leaving aside unary and binary operators +,-,*,... ,
to which extent are opcodes and operators interchangeable?:

  a) Can I use opcodes with one output value in expressions?
     (for example ar=foscil(xamp,....) )
  b) Can I use the opcode syntax for operators?
     (for example ao sin ai)
  c) What is the reason to distinguish between them?


2) Is the following grammar adequate for csound expressions?

Expr   := Expr LogOp Clause  |  Clause

LogOp  := '&&' | '||'

Clause := Clause TermOp Term  |  Term

TermOp := '+' | '-'

Term   := Term FactOp Factor  |  Factor

FactOp := '*' | '/' | '%'

Factor := '(' Expr ')'
       |  ( '+' | '-' ) Expr
       |  '(' Expr CmpOp Expr '?' Expr ':' Expr ')'
       |  Variable
       |  Function '(' Params ')'

CmpOp  := '==' | '!=' | '<' | '<=' | '>' | '>='

Variable := an identifier

Function := an operator as sin or even an opcode (depending on answer to 1)

Params := Params ',' Expr | Expr





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