**Disclaimer** This is a ** guide** to the AMPL syntax only. For a comprehensive reference to the AMPL language see AMPL: A Modeling Language for Mathematical Programming.

- Commenting
- Using symbolic
- Sets
- Variables
- Parameters
- Expressions
- Objective Functions
- Constraints
- Logical Statements
- Looping Statements
- Displaying and Printing
- Miscellaneous AMPL Commands

The `#`

is used for commenting, any characters on a line after the `#`

are ignored by AMPL.

# The set of all possible ingredients for the cat food set INGREDIENTS;

The Surfboard Production Problem

param Supply {MATERIALS}; # The supply of each raw material param Recipe {MATERIALS, SURFBOARDS}; # The "recipe" for making surfboards

The `symbolic`

keyword is used to create parameters that represent character strings. Usually they are used to represent members of 1-dimensional sets or part of a *tuple* for multi-dimensional sets. However, they can also be used to represent file names or to automatically build labels (for entry in a set, for example).

param gotcha symbolic within SET; for {s in SET} { if then let gotcha := s; } # gotcha now contains the (last) element in SET that satisfies the condition

set SET1; set SET2; set TWO_D_SET within SET1 cross SET2; param got_one symbolic within SET1; param got_two symbolic within SET2; for {(s, t) in TWO_D_SET} { if then { let got_one := s; let got_two := t; } } # (got_one, got_two) now contains the (last) element in TWO_D_SET # that satisfies the condition

To build labels for set elements you need a `symbolic`

parameter and the parts of the label. You can then "glue" the parts of the label together by enclosing the label within `(`

and `)`

and joining the parts with `&`

. The parts can be set elements, strings or numbers. Numbers are converted to strings using the %g format from printf .

param name symbolic; let SUPPLY_NODES := {}; for {s in SUPPLY_LOCATIONS} { let name := (s & '-Woodchips'); let SUPPLY_NODES := SUPPLY_NODES union {name}; let Supply[name] := MaterialSupply[s, 'Woodchips']; let {d in DEMAND_NODES} Cost[name, d] := TransportationCost[s, d]; let dummyDemandCost[name] := DisposalCost['Woodchips']; }

-- MichaelOSullivan - 27 Feb 2008

Topic revision: r9 - 2008-04-02 - MichaelOSullivan

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