example.mdx

title	Example program | ethdebug/format/program
sidebar_label	Example program
sidebar_position	3

import { ProgramExampleContextProvider, useProgramExampleContext, SourceContents, Opcodes, Viewer } from "@theme/ProgramExample";

Example program

<ProgramExampleContextProvider sources={[{ id: 0, path: "PaidIncrementer.eg", language: "examplelang", contents: `name PaidIncrementer;

// define storage layout to include variable // at slot 0 storage { [0] storedValue: uint256; }

// runtime logic code { // require fee for incrementing if (msg.callvalue < 3 finney) { return; }

let localValue = storedValue + 1; storedValue = localValue; } `}]} instructions={[ { operation: { mnemonic: "PUSH6", arguments: ["0x02ba7def3000"], }, context: ({ findSourceRange }) => ({ code: findSourceRange("3 finney"), variables: [{ identifier: "storedValue", type: { kind: "uint", bits: 256 }, pointer: { location: "storage", slot: 0 }, declaration: findSourceRange("[0] storedValue: uint256") }], remark: "hexadecimal for 3 finney" }) }, { operation: { mnemonic: "CALLVALUE" }, context: ({ findSourceRange }) => ({ code: findSourceRange("msg.callvalue"), variables: [{ identifier: "storedValue", type: { kind: "uint", bits: 256 }, pointer: { location: "storage", slot: 0 }, declaration: findSourceRange("[0] storedValue: uint256") }], }) }, { operation: { mnemonic: "LT" }, context: ({ findSourceRange }) => ({ code: findSourceRange("msg.callvalue < 3 finney"), variables: [{ identifier: "storedValue", type: { kind: "uint", bits: 256 }, pointer: { location: "storage", slot: 0 }, declaration: findSourceRange("[0] storedValue: uint256") }], }) }, { operation: { mnemonic: "PUSH1", arguments: ["0x13"] }, context: ({ findSourceRange }) => ({ code: findSourceRange("if (msg.callvalue < 3 finney) {\n return;\n }"), variables: [{ identifier: "storedValue", type: { kind: "uint", bits: 256 }, pointer: { location: "storage", slot: 0 }, declaration: findSourceRange("[0] storedValue: uint256") }], }) }, { operation: { mnemonic: "JUMPI" },

  context: ({ findSourceRange }) => ({
    code: findSourceRange("if (msg.callvalue < 3 finney) {\n    return;\n  }"),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }],
    remark: "jump to end unless sufficient fee"
  })
},
{
  operation: {
    mnemonic: "PUSH0"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("storedValue", { after: "localValue =" }),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }],
    remark: "push stack slot of state variable"
  })
},
{
  operation: {
    mnemonic: "SLOAD"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("storedValue", { after: "let localValue" }),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }],
  })
},
{
  operation: {
    mnemonic: "PUSH1",
    arguments: ["0x01"]
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("1"),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }],
  })
},
{
  operation: {
    mnemonic: "ADD"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("let localValue = storedValue + 1;"),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }, {
      identifier: "localValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "stack",
        slot: 0
      },
      declaration: findSourceRange("let localValue")
    }],
  })
},
{
  operation: {
    mnemonic: "PUSH0"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("storedValue ="),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }, {
      identifier: "localValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "stack",
        slot: 1
      },
      declaration: findSourceRange("let localValue")
    }],
  })
},
{
  operation: {
    mnemonic: "SSTORE"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("storedValue = localValue;"),
    variables: [{
      identifier: "storedValue",
      type: {
        kind: "uint",
        bits: 256
      },
      pointer: {
        location: "storage",
        slot: 0
      },
      declaration: findSourceRange("[0] storedValue: uint256")
    }],
  })
},
{
  operation: {
    mnemonic: "JUMPDEST"
  },
  context: ({ findSourceRange }) => ({
    code: findSourceRange("return;"),
    remark: "skip to here if not enough paid"
  })
}

]}

This page helps illustrate the program schema's key concepts by offering a fictional pseudo-code example and its hypothetical compiled program.

Assume this fictional [somewhat] high-level language expects one contract per source file, where each contract defines its storage layout, high-level logic, and other metadata as top-level statements or blocks.

The following source code might be used to define a contract that increments a state variable if the caller pays at least 1 finney (0.001 ETH).