Constant Expressions

A constant expression is made up of explicit constants and parameters and the FORTRAN operators. Each operand is either itself another constant expression, a constant, a symbolic name of a constant, or one of the intrinsic functions called with constant arguments.

Examples: Constant expressions:

	PARAMETER (L=29002), (P=3.14159), (C='along the ') 
	PARAMETER ( I=L*2, V=4.0*P/3.0, S=C//'riverrun' ) 
	PARAMETER ( M=MIN(I,L), IA=ICHAR('A') ) 
	PARAMETER ( Q=6.4Q6, D=2.3D9 ) 
	K = 66 * 80 
	VOLUME = V*10**3 
	DO I = 1, 20*3 

There are a few restrictions on constant expressions:

• Constant expressions are permitted wherever a constant is allowed, except they are not allowed in DATA or standard FORMAT statements.

• Constant expressions are permitted in variable format expressions. @

• Exponentiation to a floating-point power is not allowed; a warning is issued.

  Example: Exponentiation to a floating-point power is not allowed:

  ---

  demo% cat ConstExpr.f 
  	parameter (T=2.0*(3.0**2.5)) 
  	write(*,*) t 
  	end 
  demo% f77 ConstExpr.f 
  ConstExpr.f: 
   MAIN: 
  "ConstExpr.f", line 1: Warning: 
  		parameter t set to a nonconstant 
  demo% a.out 
      31.1769 
  demo%

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