Comparison of ALGOL 68 and C++

The nearest living sibling to ALGOL 68 may be C++, making this a good comparison candidate:

C++ doesn't have:

• PROC - first class nested functions (emulation due to local definitions of class-types, which then could be functors) ,
• OP and PRIO - definable operator symbols and priorities,
• garbage collection,
• use before define,
• formatted transput using complex formatting declarations,
• := - assignment operation symbol (to avoid confusion with equal sign),
• array (and slice operations on them, but in layered libraries),
• automatic UNIONs,
• CASE expressions,
• nonlocal GOTO
• intuitive declaration syntax due to its origin from C.

ALGOL 68 doesn't have:

• public/private access protection,
• overloaded procedures (in contrast to operators),
• explicit memory deallocation,
• forward declarations,
• textual preprocessing (eg macros),
• confusion between reference- and pointer-style,
• comment lines (only bracketed comments),
• hierarchical classes.

Code Example

Mode declaration

A new mode (type) may be declared using a mode declaration:

int max=99;
mode newtype = [0:9][0:max]struct (
   long real a, b, c, short int i, j, k, ref real r
);

This has the similar effect as the following C++ code:

const int max=99;
typedef class 
{ 
    double a, b, c; short i, j, k; float &r;
} newtype[9+1][max+1];

Note that for ALGOL 68 only the newtype name appears to the left of the equality, and most notably the construction is made - and can be read - from left to right without regard to priorities.

External references

• A comparison of PASCAL and ALGOL 68 - Andrew S. Tanenbaum - June 1977.
• Orthogonal language design - Apr 2004 - retrieved May 10, 2007
• How Solve the Dangling Else? - Apr 2004 - retrieved May 10, 2007
• A comparison of Pascal, C, C++ and Algol68: Types, cont Type system, Type checking, Type safety, Type conversion, Primitive types, Aggregate types: arrays - Apr 2004 - retrieved May 10, 2007
• Arrays in Algol68 - Apr 2004 - retrieved May 10, 2007